One possible workaroud for spell checking is the following:

Modify the default english dictionary:

Default dictionary is located in the following directory ...\Zotero\dictionaries\ and is made up of two files en-US.aff and en-US.dic.

You need to find the two files in the desired language, usually *.aff and *.dic are open source files used in Open Office, thus the first place to search is you local Open Office support site.

When you find your desired language pair of files just rename them accordingly with the installed Zotero dictionaries, ie:rename the files to en-US.aff and to en-US.dic. Look carefully to use the hyphen punctuation mark to separate low and high case languange ID.

Now make a backup of the original language and overwrite with your "disguised" english language files the original ones locate in ...\Zotero\dictionaries\.

Stard Zotero and check spell checking, should work.

Please note that Zotero update overwrite the workaround therefore you must redo the procedure after Zotero update.

Bitnik

Yes please! I agree with guidogorgoni that simply preventing Zotero updater from wiping out the workarounds would be an excellent compromise.